<template>
  <div class="pagination">
    <button @onclick="changePageNo(pageNo - 1)" :disabled="pageNo === 1">
      上一页
    </button>
    <button v-show="startAndEnd.start > 1" @click="changePageNo(1)">1</button>
    <span v-show="startAndEnd.start > 2">...</span>
    <button
      v-for="(_, index) in startAndEnd.end - startAndEnd.start + 1"
      :key="_"
      :class="{ active: pageNo === index + startAndEnd.start }"
      @click="changePageNo(index + startAndEnd.start)"
    >
      {{ index + startAndEnd.start }}
    </button>
    <button v-show="startAndEnd.end < totalPage - 1">···</button>
    <button
      v-show="startAndEnd.end < totalPage"
      @click="changePageNo(totalPage)"
    >
      {{ totalPage }}
    </button>
    <button @click="changePageNo(pageNo + 1)" :disabled="pageNo === totalPage">
      下一页
    </button>
    <span style="margin-left: 30px">共{{ totalPage }}条</span>
  </div>
</template>

<script>
export default {
  name: 'Pagination',
  // data() {
  //   return {}
  // },
  props: ['total', 'pageNo', 'pageSize', 'continues', 'changePageNo'],
  // props: {
  //   total: {
  //     type: Number,
  //     default: 1
  //   },
  //   pageNo: {
  //     type: Number,
  //     default: 1
  //   },
  //   pageSize: {
  //     type: Number,
  //     default: 0
  //   },
  //   continues: {
  //     type: Number,
  //     default: 3
  //   }

  computed: {
    // 1. 计算总页码
    totalPage() {
      // 父组件传递过来的数据，就相当于当前组件中data中的数据
      let { total, pageSize } = this
      return Math.ceil(total / pageSize)
    },
    // 2. 计算连贯页码的起始和结束
    startAndEnd() {
      let { pageNo, continues, totalPage } = this
      let start, end
      // start = pageNo - Math.trunc(continues / 2)
      // end = pageNo + parseInt(continues / 2)
      // return { start, end }
      if (continues > totalPage) {
        start = 1
        end = totalPage
      } else {
        start = pageNo - Math.trunc(continues / 2)
        end = pageNo + parseInt(continues / 2)
        if (start < 1) {
          // 如果起始页小于了1
          start = 1 // 起始页必须是1
          end = continues // 结束页就是continues
        }
        if (end > totalPage) {
          // 如果结束页大于了总页码
          end = totalPage // 结束页必须是总页码
          start = totalPage - continues + 1 // 开始页要从后往前算
        }
      }
      return { start, end }
    },
  },
}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #c81623;
      color: #fff;
    }
  }
  span {
    display: inline-block;
    line-height: 28px;
    font-size: 14px;
    color: gray;
    vertical-align: middle;
  }
}
</style>
